Bonjour !
I.
g)
-3(-x+4) - 2(7x-5) = 3x - 19
<=> -3*(-x)+(-3)*4 + (-2)*7x +(-2)*(-5) = 3x - 19
<=> 3x+ (-12) + (-14x)+10 = 3x - 19
<=> -11x -2 = 3x - 19
<=> -2 +19= 3x +11x
<=> 17= 14x
x = 17/14
d)
-7x+4 = -x-14
<=> 4 + 14 = -x+7x
<=> 18 = 6x
<=> x = 18/6 = 3
h)
(2x+1)(-x-4) = x(-2x+6)
<=> -2x² - 8x - x - 4 = -2x² + 6x
<=> - 8x - x - 4 = 6x
<=> -9x - 4 = 6x
<=> -4 = 6x+9x
<=> 15x = -4
<=> x = -4/15
II. Équations produit nul.
a)
(2x-4)(-x+3) = 0
Donc soit :
2x-4 = 0 ; 2x = 4 ; x = 4/2 ; x=2
soit :
-x+3 = 0 ; -x = -3 ; x = 3
b)
(-x+9)(7x-21) = 0
-x+9 = 0 ; -x = -9 ; x = 9
7x - 21 = 0 ; 7x = 21 ; x = 21/7 ; x = 3
c)
x(-3x + 6) = 0
x = 0
-3x+6 = 0 ; -3x = -6 ; x = -6/(-3) ; x = 2
Voilà !
